How do I put a image inside of every brick on the brick texture?
It is not possible to map image textures using a Brick Texture node

For texture placemanet you need texture coordinates. Brick texture outputs only colors. So it is not possible to map any images to the colors of the brick texture.  

However, you can manipulate texture coordinates using Math nodes

Texture coordinates are only sort of gradients going in some direction from -&infin; to + &infin; and you can manipulate them with all sorts of math functions: 



So using various maths functions you can construct the same brick pattern out of
the texture coordinate gradients and use that to map any image you wish in the same pattern: